Scientists believe that farm fertilizer containing the chemical phosphorus recently caused unsafe levels of toxic algae in drinking water in Toledo. One of the main sources of phosphorus is farm runoff. But phosphorus is essential to crops.

For Ohio Public Radio, WOSU's Mandie Trimble reports that Ohio State University scientists are looking for a solution.

Ohio State soil scientist Libby Dayton is working with the U.S. Department of Agriculture to find out just how much fertilizer drains out of Ohio farm fields.

Dayton is studying 30 farms in the Scioto, Grand Lake St. Marys and Western Lake Erie Basin watersheds. The latter two have the most serious problems with toxic algae.

“We have monitoring equipment at the edge of their field, and we’re collecting, on most fields, a surface or tile runoff," Dayton says. "So we’re collecting all the water that’s coming off of their fields.”

This is the project’s second year. In addition to collecting runoff and soil samples, Dayton says the farmers share their field management methods.

“We can see everything they’re doing on the field and relate that to what we see coming off the field on an event basis, every rainfall event, every runoff event," Dayton says. "And that helps us quantify what was going on in the field at that time and how it relates to what we see coming off the field.”

The Phosphorus Risk Index, or P Index, was originally created to assess runoff risk, but now it provides management practices and regulations. Farmers use it as a guide to develop fertilizer plans for their crops.

Dayton says updating the index will be invaluable to farmers as they try to reduce phosphorus runoff.

Dayton says farners are "asking us, 'What can we do, what can we change, and will it really help?' And so that’s the tool that we’re ultimately trying to deliver to the farmer.”

Trying to conserveBret Davis is a farmer from Delaware.

“We have a mix of corn and soybeans," Davis says. "We farm about 3,800 acres between my stepson and myself.”

Davis is not part of the P Index study, but he is very interested in its findings. Davis, who began farming in 1978, says fertilizing practices have changed considerably just in the last five years.

“For every half acre in our field, we know exactly what goes on that half acre so that we’re not putting on any more than we need but we put on enough to grow that crop,” Davis says.

Davis says he planted large filter strips around a stream near his soybean field to quell the runoff.

Davis drives his four wheeler across the street to a dirt path. Soybeans are planted on either side of it.

Field strips help“As you see here this is an old quarry," Davis says. "This is the starting sides of the stream. And here on the backside, you can see as the stream goes out of the quarry, so you have the filter strips that are on both sides of that stream.”

The field strips Davis talks about are tall, natural grasses he planted about six years ago. They are between 30 and 60 feet wide.

“It doesn’t look like much, but it’s just a natural buffer that we keep nutrients out of the streams because this stream feeds into the Olentagny,” Davis says.

OSU’s Libby Dayton has collected thousands of samples in the edge of field testing. She says so far, the analysis has shown significant runoff differences between farms.

“By seeing that, I think we’ll be able to offer some really good insights to help reduce for the farmers that may be having a problem," Dayton says. "The good news is that many of the farmers, there’s very, very little coming off the fields. We have a lot of farmers that are doing a really good job and already initiating best management practices.”